An overmolded motor vehicle front panel is already known, e.g. from patent FR 2 719 014 filed in the name of the Applicant, and comprising a metal cross-member having each of its ends inserted in a mold so that a portion of the cross-member projects from the mold, with the cross-member having plastics materials overmolded thereon in order to form support parts for headlight units.
Under such circumstances, the mold is sealed by a portion of the wall of the mold co-operating with the cross-member. It has been found that the mold is then not sealed in satisfactory manner. The cross-member forms an integral portion of the overmolded part that is obtained and must therefore not be subjected to excessive pressure in order to avoid damaging it.
When the sealing is not satisfactory, the plastics material delivered under pressure to the inside of the mold tends to escape towards the outside of the mold, in particular while the pressure inside the mold is high, e.g. during the stage of compacting the molding by injection.
Leaks of material to the outside of the mold degrade the quality of the overmolded part.